1. Field of the Invention
The present invention relates to improvement in an internal combustion engine in which a strainer is provided in a sump.
2. Description of Background Art
A sump of an internal combustion engine usually is provided with a strainer formed in a mesh form and configured to remove foreign substances contained in an oil. See, for example, Japanese Patent Application Publication No. 2005-9346, FIG. 2.
As illustrated in FIG. 2 of Japanese Patent Application Publication No. 2005-9346, an oil pan to store an oil is formed at a lower portion of a crankcase, and a strainer (9) is attached to an upper wall (19) (the number in parentheses indicates a reference numeral described in Japanese Patent Application Publication No. 2005-9346; the same applies to the following) in this oil pan, an oil drain port (23) is formed in a bottom wall (22) of the oil pan coaxially with the strainer (9) with a drain bolt (16) fastened to the oil drain port (23). The strainer (9) is supported by the drain bolt (16).
In the technique described in Japanese Patent Application Publication No. 2005-9346, since the oil drain port (23) is arranged coaxially with the strainer (9), air may possibly enter the strainer (9) from the bottom wall (22) of the oil pan during an oil change. In addition, the oil returning to the oil pan after circulating in the engine contains bubbles (air), and the bubbles (air) may possibly enter the strainer (9). Thus, there is a demand for a technique to make air less likely to enter the strainer (9).